.demo{
    border: 1px solid red;
    position: relative;
}
.small_box{
    display: inline-block;
    position: relative;
    border: 1px solid #eee;
    margin: 30px 0 0 30px;
    cursor: pointer;
}
.small_box img{
    width: 400px;
    height: 255px;
}
.mask{
    display: none;
    position: absolute;
    width: 160px;
    height: 120px;
    background: #ffffcc;
    opacity: 0.5;
    filter: alpha(opacity=50);
}
.big_box{
    border: 1px solid #eee;
    overflow: hidden;
    display: none;
    width: 410px;
    height: 308px;
    position: absolute;
    top: 30px;
    left: 460px;
}
.big_box img{
    width: 1024px;
    height: 654px;
    position: absolute;
}
